Habitat assessment, Missouri River at Hermann, Missouri

Abstract

This report documents methods and results of aquatic habitat assessment in the Missouri River near Hermann, Missouri. The assessment is intended to improve understanding of spatial and temporal variability of aquatic habitat, including habitats thought to be critical for the endangered pallid sturgeon (Scaphirhynchus albus). Physical aquatic habitat -depth, velocity, and substrate -was assessed around 9 wing dikes and adjacent to the U.S. Route 19 bridge, at discharges varying from 44,000 cubic feet per second (cfs) to 146, 000 cfs during August 2000 -May, 2001. For the river as a whole, velocities are bi-modally distributed with distinct peaks relating to navigation channel and wing-dike environments. Velocities predictably showed an increasing trend with increasing discharge. Substrate within wing dikes was dominated by mud at low discharges, whereas the navigation channel had patches of transporting sand, rippled sand, and coarse sand. Discharges that overtopped the wing dikes (about 93,000 cfs, March 2001) were associated with increases of patchy sand, rippled sand, and coarse sand within the wing dikes. When flows were substantially over the wing dikes (146,000 cfs, May 2001) substrates within most wing dikes showed substantial reorganization and coarsening.The habitat assessment provides a geospatial database that can be used to query wing dikes for distributions of depth, velocity, and substrate for comparison with fish samples collected by US Fish and Wildlife Service biologists (Grady and others, 2001). In addition, the assessment documented spatial and temporal variation in habitat within the Hermann reach and over a range of discharges. Measurable geomorphic change -alteration of substrate conditions plus substantial erosion and deposition -was associated with flows equaled or exceeded 12-40% of the time (40-140 days per year). Documented geomorphic change associated with high-frequency flows underscores the natural temporal variability of physical habitat in the Lower Missouri River.

Fish Assemblages at Engineered and Natural Channel Structures in the Lower Missouri River: Implications for Modified Dike Structures

“…Dike habitat was defined as the area extending downstream of the dike to the next dike or a distance of 250 m, whichever was shorter, and extending from the bank to 50 m into the navigational channel (Jacobson et al , ). Wing dikes are straight rock structures constructed perpendicular to the main current and located along inside river bends (Jacobson et al , ). The greatest depths are found near the main channel margins and at scour holes (i.e.…”

“…Substrate associated with wing dikes typically consists of mud, sand, coarse sand, rippled sand, and gravel but is highly influenced by velocity and discharge that varies throughout the structure. L‐dikes are shaped like an ‘L’ with the short arm extending to the bank and the long arm parallel to the main current pointing downriver (Jacobson et al , ). Most L‐dikes are located near outside river bends and channel crossovers that utilize the long arm to protect river banks from high water velocities.…”

“…All physical habitat characteristics associated with an engineered dike structure can be influenced by discharge and flood events (Papanicolaou et al , ). On a broad temporal scale, the physical habitat characteristics are resilient because dike structures are static features (Jacobson et al , ). The U.S. Army Corps of Engineers has been notching L‐ and wing dikes since 2004 to diversify fish habitats (Jacobson et al , ).…”

“…In contrast, sand bar habitats represent the most natural habitats remaining in the lower Missouri River. They are dominated by a sand substrate and gradient <10°, which differ from engineered dike structures where the gradient ranges from 20° to 40° with more variable substrate composition (Jacobson et al , ; Laustrup et al , ). Channel sand bars were also more susceptible to alteration by even moderate flows than dike structures (Jacobson et al , ).…”

Evaluation of the Missouri River shallow water habitat using a 2D‐hydrodynamic model

“…Several studies have investigated the SWH in the Missouri River (e.g. Jacobson et al ., 2002, 2004; Elliott et al ., 2004; Elhakeem and Papanicolaou, 2007). However, the majority of these studies were limited to SWH around single dikes during single flow events, ignoring seasonal changes in discharge and the added resistance to flow that can develop from the presence of multiple dikes along a stream reach.…”